Silver halide emulsions containing polyisothiuronium salts as stabilizers



United States Patent 3,375,115 SILVER HALIDE EMULSIONS CONTAINING POLY- ISOTHIURONIUM SALTS AS STABILIZERS William F. Smith and Bernard D. Illingsworth, Rochester,

N.Y., assignors to Eastman Kodak Company, Rochester, N.Y., a corporation of New Jersey No Drawing. Filed Feb. 10, 1965, Ser. No. 431,701 10 Claims. (Cl. 96-109) This invention relates to photographic elements, and more particularly to the stabilization of photographic elements.

In one embodiment of our invention, we provide silver foggants for photographic silver halide emulsions. Another object of our invention is to provide photographic silver halide emulsions containing certain polymers which function to stabilize developed silver images. A further object of our invention is to stabilize photographic silver images wit-h certain polymers. Other objects of our invention will appear herein.

In one embodiment of our invention, we provide silver halide emulsions containing a polymer having repeating units represented in the following formula:

wherein R represents H or a lower alkyl group, such as methyl, ethyl, propyl or hutyl, preferably methyl or ethyl; R represents an alkylene group preferably of 2 to carbon atoms, but which may contain up to 12 or more carbon atoms, such as ethylene, propylene, butylene, hexylene, octylene and dodecylene; A is an anion, such as halide, p-toluene sulfonate or methanesul-fonate; and n is a whole number, such as 5 to 100,000 or more. We have found that the above polymers function as antifoggants in photographic silver halide emulsions. We have also found that silver images prepared from silver halide emulsions containing the above polymers are effectively stabilized against oxidative degradation, and that the polymers employed in the invention provide desirable cold-tone silver images.

In another embodiment of our invention, the silver image of a photographic element is stabilized against oxidative degradation by bathing the photographic element in a solvent solution of the isothiuronium salt containing polymers described above.

Our invention will be further illustrated in the following examples. Example 1 shows the antifoggant activity in photographic emulsions of the polymers used in the invention.

EXAMPLE 1 A sulfur and gold sensitized, negative speed gelatin silver bromoiodide emulsion was prepared and divided into several portions. Various concentrations of copoly (N,N dimethylacrylamide ethyl acrylate 2[2 (methacryloyloxy)ethyl]isothiuronium p toluene sulfonate) (50:30:20 by weight) referred to as Polymer A in Table I, and copoly[N,N-dimethylacrylamide-2[Z-(methacryloyloxy) ethyl] isothiuronium methanesulfonate] 50: 3 0:20 by weight) referred to as Polymer B in Table II, were each incorporated into separate portions of the emulsion. The resulting emulsions were coated on a support at the rate of 432 mg. silver and 980 mg. gelatin per square foot, exposed and developed for 5 minutes in Kodak Developer DK-50. The samples were incubated for one week at 100 F. and 50% relative humidity. The results are shown in Table I.

3,3 75,1 15 Patented Mar. 26, 1968 TABLE I Concentration Fog Copolymer per grams gelatin (g.) Fresh Incubated Control 25 68 Polymer A.-- 5. 14 20 D0 10 14 24 Polymer B 5 .18 27 Do 10 11 20 As may be seen in the above table, emulsions in accordance with the invention have substantially less fog than control emulsions which do not contain polymers having isothiuronium salt groups.

Examples 2-5 illustrate the superior stability of silver images produced from silver halide emulsions containing polymers having isothiuronium salt groups.

EXAMPLE 2 Ten grams per mole of silver of copoly[N,N-dimethylacrylamide-Z-[Z (methacryloyloxy)ethyl]isothiuronium methanesulfonate] (50:30:20 by weight) were added to a panchromatic, sulfur and gold sensitized silver chlorobromide gelatin emulsion just prior to coating on a cellu lose triacetate base. After exposure and processing, the film had a cold-toned image. The image was placed in hydrogen peroxide vapor for 24 hours and showed good resistance to oxidation, whereas a control which did not contain the polymer was severely damaged by this test.

EXAMPLE 3 Ten grams of poly(2[2-(methacryloyloxy)ethyl]isothiuronium met-hanesulfonate were added to a sensitized emulsion, exposed and processed. The image had a colder tone than that of the control, and showed outstanding resistance to hydrogen peroxide vapor attack when tested as described in Example 2.

EXAMPLE 4 Ten grams of copoly(N,N-dimethylacrylamide-ethyl acrylate-2-[2 (methacryloyloxy)ethyl]isothiuronium ptoluene sulfonate) (50:30:20 by weight) were substituted for the polymer employed in Example 3. As compared with the control, the image was colder toned and had superior resistance to hydrogen peroxide vapor attack when tested as described in Example 2.

EXAMPLE 5 Ten grams of poly(2-[3-(methacryloyloxy)propyl] isothiuronium p-toluene sulfonate) were substituted for the polymer employed in Example 3. The image had a colder tone than the control, and had good resistance to hydrogen peroxide vapor attack when tested as described in Example 2.

The stabilization of silver photographic images by contacting the image with a polymer having isothiuronium salt groups is demonstrated in Example 6.

EXAMPLE 6 A one percent solution of copoly(N,N-dimethylacrylamide-ethyl acrylate 2[2 (methacryloyloxy)ethyl]isothiuronium methane sulfonate) (50:30:20 by weight) in water was used to bathe "two strips of an exposed, developed and fixed panchromatic sulfur and gold sensitized silver chlorobromide microfilm containing silver images. The strips were bathed in the solution for 5 minutes at 68 'F. One strip of the treated film was then rinsed for one second in water, the other was rinsed for 5 minutes in running water, and both were dried at 68 F. Both strips were then subjected to a 24-hour hydrogen peroxide vapor test in the presence of acetic acid vapor. The strips were both essentially free from peroxide attack, whereas an untreated control was severely attacked.

The polymers useful in this invention may consist solely of repeating units which are isothiuronium salts. Copolymers are also useful in which at least one-third of the repeating units are isothiuronium salts; the remaining repeating units may be any suitable divalent moiety, such as those represented by the formula:

wherein A, B, D, and E are substituents which do not exert any detrimental effect on photographic emulsions, or are substituents which are not detrimental to silver images when the polymers are employed in post-processing baths.

It should be noted that some of the copolymers employed in the examples are described by weight ratios of reactants. In all of these copolymers, at least one-third of the repeating units are isothiuronium salts.

The polymers employed in this invention may be prepared in any convenient manner, such as by the method described by Dykstra and Smith in their patent application filed on the same date as the present application. A convenient method is to prepare a monomer having the formula:

wherein R is H or alkyl, R is alkylene and A is an anion, by forming a sulfonate ester of a compound having the formula:

and treating the reaction product with thiourea. The monomer may then be polymerized alone or with a copolymerizable monomer.

The polymers employed in this invention are not removed from photographic emulsions during processing, but remain in the finished product functioning to promote image stability, for example, against oxidative degradation.

The most useful concentration range of the polymers in photographic silver halide emulsions, to provide antifoggant activity and image stability, is from about 1 to 20 grams polymer per mole of siver; preferably, we employ about 5 to grams of polymer per mole of silver.

If desired, silver images may be stabilized by bathing in a solution containing the polymers described above.

' The duration of effective treatment varies according to the particular polymer employed and the concentration thereof in the solution. Any solvent may be employed which is not detrimental to the photographic element.

This invention is broadly applicable to photographic silver halide emulsions and to stabilizing the silver image obtained from them. It has special utility for sensitized, particularly sulfur-gold sensitized, silver chlorobromide emulsions, e.g., microfilms having such emulsions.

The invention has been described in detail with particular reference to preferred embodiments thereof, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention as described hereinabove and as defined in the appended claims.

We claim:

1. A photographic silver halide emulsion having incorporated therein a stabilizing quantity of a polymer in which at least one-third of the repeating units have the following formula;

wherein R is selected from the group consisting of hydrogen and alkyl, R is alkylene, n is a whole number, and A is an anion.

2. A photographic silver halide emulsion having incorporated therein a stabilizing quantity of copoly(N,N- dimethylacrylamide-ethyl acrylate 2 [Z-(methacryloyloxy) ethyl]isothiuronium salt, at least one-third of the repeating units of the polymer being isothiuronium salt units.

3. A photographic silver halide emulsion having incorporated therein a stabilizing quantity of poly(2[2-methacryloyloxy) ethyl] isothiuronium salt.

4. A photographic silver chlorobromide emulsion having incorporated therein a stabilizing quantity of copoly (N,N-dimethylacrylamide-ethyl acrylate-Z [2 (methacryloyloxy)ethyl]isothiuronium p-toluene sulfonate, at least one-third of the repeating units of the polymer being isothiuronium salt units.

5. A photographic silver halide emulsion having incorporated therein a stabilizing quantity of poly(2-[3- (methacryloyloxy propyl] isothiuronium salt.

6. The method of stabilizing the silver image of a photographic element which comprises bathing the photographic element in a solvent solution of a polymer in which at least one-third of the repeating units have the following formula:

wherein R is selected from the group consisting of hydrogen and alkyl, R is alkylene, n is a whole number, and A is an anion.

7. The method of stabilizing the silver image of a photographic element which comprises bathing the photographic element in a solvent solution of copoly(N,N- dimethylacrylamide-et'hyl acrylate 2 [Z-(methacryloyloxy)ethyl]isothiuronium salt), at least one-third of the repeating units of the polymer being isothiuronium salt units.

8. The method of stabilizing the silver image of a photographic element which comprises bathing the photographic element in a solvent solution of poly(2-[2-(methacryloyloxy) ethyl] isothiuronium salt) 9. The method of stabilizing the silver image of a photographic element which comprises bathing the photographic element in a solvent solution of copoly(N,N-dimethylacrylamide-ethyl acrylate 2 [Z-(methacryloyloxy)ethyl]isothiuronium p-toluene sulfonate), at least one-third of the repeating units of the polymer being isothiuronium salt units.

10. The method of stabilizing the silver image of a photographic element which comprises bathing the photographic element in a solvent solution of poly(2-[3-(methacryloyloxy propyl] isothiuronium salts) References Cited UNITED STATES PATENTS N0 References Cited.

NORMAN G. TORCHIN, Primary Examiner.

I. R. EVERETT, Assistant Examiner. 

1. A PHOTOGRAPHIC SILVER HALIDE EMULSION HAVING INCORPORATED THEREIN A STABILIZING QUANTITY OF A POLYMER IN WHICH AT LEAST ONE-THIRD OF THE REPEATING UNITS HAVE THE FOLLOWING FORMULA: 